The present invention relates to releasable mounting systems for vehicle accessories which will release the accessory upon impact to prevent injury and, more particularly, to a breakaway mounting system especially useful with rearview mirrors which is reusable after release and compatible with existing vehicle supports, but is simplified and more reliable than prior known assemblies.
Breakaway rearview mirror mounting systems in which the mirror is released from a supporting structure in the vehicle upon receipt of an impact or during an accident are well known. Many countries of the world require the use of such breakaway assemblies to meet minimum vehicle standards. However, prior known breakaway systems have often provided inconsistent installation and/or release forces even though manufactured to the same tolerances. When such systems are installed on vehicles, some will release at higher loads than others and/or require greater installation effort than others thereby creating the possibility of injury to vehicle occupants as well as difficulties in manufacture and/or higher part rejection rates and higher costs.
In addition, many prior known breakaway mirror mounting systems have not been designed for reinstallation after release. In such systems, frangible or other parts useful only one time are included such that the entire assembly must be replaced after an accident, other release due to an impact, or even removal for repair. As a result, the costs for using these systems are significantly higher.
In other systems, performance after reinstallation is substandard. In many prior systems, springs or resilient members included in the system are not caused to "yield" prior to release. Causing a spring to "yield" establishes a predetermined spring force. However, when such "yield" occurs only upon release of the assembly during an accident or the like, the spring force will be less upon reinstallation. Thus, tight, consistent retention of the rearview mirror or other accessory after reinstallation is impossible without resultant vibration and blurring of images in the mirror. Further, in many cases, the assembly must be entirely replaced even though the ability to reinstall and use is intended.
In yet other prior known breakaway systems, the impact directions for which release from the vehicle is allowed has often been limited. For example, some assemblies allow release only when impacted by an object or person within the vehicle moving upwardly and/or toward the windshield and against the assembly upon sudden deceleration. However, the increased use in vehicles of supplemental vehicle occupant restraint systems, known as airbags, has created additional hazards since the release of one or dual airbags for the driver and/or front seat passenger can trap the rearview mirror rearwardly of the airbag when the mirror is mounted in the center of the windshield. Proper release is prevented if the mirror is struck during an accident, while the airbag or bags are inflated. Thus, a need was recognized for breakaway mirror mounting assemblies which can release from multiple directions including that caused by an expanding airbag or bags.
Apart from the above, other problems encountered with previously known breakaway rearview mirror support assemblies have included the use of a large number of related parts which not only increase manufacturing and inventory costs, but also create complex assemblies with greater possible failure modes and which require more time or are more difficult and complex to assemble and install. Moreover, many prior known breakaway assemblies have required the use of tools for installation in a vehicle thereby requiring more highly trained installers and creating additional expense. Further, set screws have been included in some assemblies. These screws can loosen during use and result in unwanted vibration and image blurring. Also, many prior known breakaway assemblies have included less than adequate retention strength in order to allow easier installation thereby compromising stability during use and again creating unwanted vibration and image blurring visible in the supported mirror.
Therefore, a need was apparent for an improved, simplified, breakaway mounting assembly for rearview mirrors and other accessories which overcomes the above problems.